2 Carts in one store?

Hello, I own comic book type stores as such i both buy and sell merchandise. I have been trying to figure out a way to basically have two carts. I want people to be able to make an order of the items they are going to be selling me (with my buy it price). How can I do this? Would multiple storefronts with CS-cart 4 solve this?

Basically you come to my website, you have one cart for buying items and one cart to put the items in your selling to me. They are the same items but different prices. I thought about just putting them in separate categories and using the quantity discounts feature to do negative prices for the items I buy but do not want to cloud up the search feature on the site.

Any advice is appreciated!